The dust particles are captured in a very light substance called Aerogel which slows the particles down without harming them.

When they strike the Aerogel, they are travelling at a speed relative to Stardust of between 10 and 26 km per second (6 to 16 miles per second).

Other suns

Astronomers believe that the dust particles come from stars elsewhere in our galaxy, where they are formed by condensation around those other suns.

"The Milky Way is awash with the stuff - just peer upward on a clear night," Brownlee said.

"You see this dark band running along the middle of it?" Brownlee adds, "That is interstellar dust, blocking the light of some stars."

Once the sample capsule is back on Earth, scientists will use an arsenal of instruments including electron microscopes, ion microprobes, atomic force microscopes, synchrotron microprobes, and laser probe mass spectrometers, to coax the interstellar grains to give up their secrets.